Range extender prototype hybrid unveiled in Japan

Mazda rotary gets new lease on life

Range extender prototype hybrid unveiled in Japan

The Mazda2 prototype runs as an electric vehicle, with an electric motor powering the wheels. But it also gets a gasoline-powered 0.33-liter rotary engine in the rear that generates power to recharge the car's lithium ion battery when the charge runs low.
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Editor's note: An earlier version of this story misidentified the first vehicle Mazda used to market a rotary engine.

YOKOHAMA, Japan -- Mazda Motor Corp. has given a new lease on life to its rotary engine in the form of a Mazda2 hatchback reconfigured as an extended-range hybrid.

The prototype runs as an electric vehicle, with an electric motor powering the wheels. But it also gets a gasoline-powered 0.33-liter rotary engine in the rear that generates power to recharge the car's lithium ion battery when the charge runs low.

Mazda showed the car Thursday at a briefing here about future drivetrain technologies. The powertrain is similar to that used in the Chevrolet Volt, another extended-range hybrid.

Mazda calls it the RE Range Extender, short for Rotary Engine Range Extender.

The unveiling came just weeks after Masamichi Kogai, Mazda's new CEO, threw cold water on the rotary engine's future, saying there were no plans for a production version.

He said sales would have to total 100,000 units a year to justify a commercial revival of the rotary. But engineers continue to tinker away with the technology, he conceded.

And the modified range-extender Mazda2 is one product of that research.

The car might help Mazda meet California's strict zero emissions requirements, said Takashi Suzuki, program manager for advanced powertrain development. California requires electric vehicles but is expected to also give credit for certain hybrids, he said.

"I would say it's an option," Suzuki said. "Some companies may add a plug-in hybrid."

The engine's chief hurdle is technical: meeting stringent emissions regulations. But using a compact version as a generator in a hybrid has advantages:

• It can run more consistently at its sweet spot, maximizing fuel economy.

• It runs quietly with little vibration.

• It can run on a variety of different fuels.

• It is small and can be packed into many different body shapes.

Mazda mounts the rotary to a generator and small fuel tank and installs the system under the Mazda2's trunk. The 75-kilowatt electric motor that drives the wheels is in front.

The lithium ion battery is tucked under the floorboards.

The idea is to alleviate the range anxiety associated with electric vehicles, the worry that you might be stranded if you're battery runs out and you can't find a plug. That's where the range extender comes in: Its onboard engine recharges the battery to keep you going.

Mazda already has a pure EV Mazda2 with a range of 200 kilometers (124 miles), but the range extender with a 10-liter (2.6-gallon) fuel tank can double that driving range.

The rotary engine had been a Mazda bragging point ever since the company became the first to market the technology, in 1967, in its Cosmo Sport/Mazda S110. 

But the company killed the powerplant last year when the last RX-8 sports car rolled off the line.

The engine is also known as the Wankel after the German engineer who invented it. A rebirth has been the subject of incessant speculation, often fueled by Mazda itself. The idea of a rotary range extender was dangled last year by then-president Takashi Yamanouchi.

While there are no production plans, Kogai told Automotive News the company hangs on to the rotary partially for sentimental reasons.

"We are the first and only manufacturer to commercialize the rotary engine," he said. "In that respect, we have some responsibility."

You can reach Hans Greimel at hgreimel@crain.com. -- Follow Hans on Twitter


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